所有员工薪水，逆序

找出所有员工当前(to_date=’9999-01-01’)具体的薪水salary情况，对于相同的薪水只显示一次,并按照逆序显示
CREATE TABLE salaries (
emp_no int(11) NOT NULL,
salary int(11) NOT NULL,
from_date date NOT NULL,
to_date date NOT NULL,
PRIMARY KEY (emp_no,from_date));

select salary from salaries
where to_date='9999-01-01'
group by salary
order by salary desc

SELECT DISTINCT salary FROM salaries WHERE to_date = '9999-01-01' ORDER BY salary DESC